I was playing on a friends realm and I had logged off of the realm and joined a single player world of the same seed that i use for creative testing. when i logged on i noticed that the sun was glitching around in the sky and eventually it was glitching between night and day. At this point i started getting hit by something even though I was in creative and eventually the game said that i was killed by a zombie even though i was still in creative. Thinking it was weird but not thinking anything of it i continued on playing in the creative world before getting back on the realm to find that i had been killed by a zombie in the server. The only conclusion I can make is that somehow my game had me logged into both the realm and the single player world simultaneously and somehow i was killed in the realm while i was actually in single player.